1. Field Of the Invention
This invention generally relates to methods of cleaning up oil spills from natural bodies of water such as oceans, seas, lakes, harbors and rivers. More specifically, this invention relates to methods for flocculating and/or agglomerating spilled oil associated with a natural body of water, such as a floating layer or film of oil and/or dispersed oil droplets, emulsions, etc., in order to facilitate subsequent physical recovery, containment, or further treatment of such oil.
2. Prior Art
Oil pollution of natural bodies of water, and especially of the ocean, has caused extensive environmental problems and ever mounting public concern. Such pollution has been caused by illegal dumping, accidents, warfare and leakage from oil drilling operations in continental shelf regions. Regardless of their cause, however, oil spills invariably produce extensive ecological and/or economic damage by destroying or tainting many forms of aquatic life and by fouling water intakes, recreational beaches, boats, fishing gear, harbor installations and the like.
Unfortunately, oil cleanup operations are both physically and technically difficult; they normally involve one or more of the following measures: (1) physical removal of the oil from the water, with or without the use of adsorbents, (2) dispersion of the oil through the use of detergents, (3) "sinking" the spilled oil and (4) burning floating oil slicks. Each of these measures has its own set of special environmental and technical considerations.
Physical removal (e.g., by "skimming" or pumping operations) is of course the most ecologically desirable remedy but, using existing technologies, it is feasible only under nearly ideal weather, water turbulence and response time conditions. Generally speaking, seas higher than about 1-2 feet, currents in excess of 2-3 knots and/or the passage of a few day's time usually makes physical removal operations largely ineffective and extremely costly.
Dispersion of spilled oil through the use of detergents can be accomplished much more quickly, but this technology has several detrimental side effects. For example, the detergents normally employed to disperse spilled oil are very often toxic to aquatic life in their own right. Moreover, their use also tends to bring the spilled oil into more intimate contact with living organisms than it might otherwise attain.
Sinking has its own set of detrimental side effects, e.g., sinking strongly retards the ultimate degradation of the oil by incorporating it into underwater sediments where anaerobic conditions may prevail. However, not all water body bottoms are anaerobic or biologically inert. For example, nearshore areas often have high levels of biological activity as evidenced by the presence of kelps, shellfish, worms, etc. in such areas. Consequently, these forms of life may be completely wiped out by "sinking" an oil spill into their delicate habitats.
Burning is of course greatly restricted by: the difficulties associated with getting "oil-on-water" fires started, ecological concerns regarding any incomplete burning of the oil and any attendant air pollution problems produced by such burning. Obviously, such burning also will be restricted by any local fire hazard considerations. Burning also represents a total economic waste of the oil.
Certain physical removal methods are accompanied by the use of adsorbents such as finely divided or porous solid materials (e.g., straw, clays, sawdust, etc.) in order to help agglomerate oil films and/or oil/water emulsions. Such agglomeration is desirable because it ultimately aids in the physical gathering of the spilled oil. In effect, agglomeration of this kind produces relatively large, thick, distinct, patches or globs of more viscous, but still "liquid", oil from those relatively thin slicks or films of oil which reside on the water's surface and/or from those finely dispersed, droplets which comprise oil/water emulsions. This agglomeration action is brought about by surface and capillary actions of these materials upon spilled oil. Various clays have been used or at least suggested for use as such oil agglomeration agents, e.g., attapulgite, bentonite, kaoln and montmorillonite are most frequently suggested.
However, cleanup operations using such clays have not been widely employed, largely because--in spite of their ability to sorb oil--such clays also tend to allow the oil to desorb in relatively short periods of time. That is to say that these clays, in the context of an oil spill on water, tend to allow the oil to desorb before the oil patches produced by them can be physically collected or otherwise treated, e.g., by chemical treatment, microorganism digestion, etc. The use of such clays, in absence of other floatable materials such as sawdust, wood chips, etc., also tends to produce agglomerated materials which may well sink. Moreover, even if a floating oil film and/or a finely dispersed oil/water emulsion can be successfully converted to relatively large droplets of oil by the use of such clays, and even if those large droplets, once formed, form distinct patches which can exist on the surface of the water for periods of time long enough to be successfully collected, the inherent problems generally associated with separating one liquid from another liquid still remain as a distinctly troublesome part of the overall cleanup problem.
For example, the "liquid from liquid" (i.e., oil from water) separation problem which must be overcome in order to clean up an oil spill generally entails picking up large volumes of water along with an agglomerated oil/clay material which has an essentially "liquid" character. In fact, a very large proportion of the total material picked up in such cleanup operations is in fact water. That is to say that oil cleanup operations which use the previously noted clays in order to agglomerate oil films and/or oil/water emulsions into larger oil droplets and/or into larger oil patches do not avoid the problem of mechanically taking up (e.g., by suction and/or pumping operations) those large volumes of water with which relatively the smaller volumes of liquid oil are associated. Consequently, various additional "oil from water" separation processes are needed to complete the overall cleanup operation. They are normally performed in tanks on board ships, barges, tenders, etc. under those relatively controlled, quiescent, conditions needed to effect the physical and/or chemical separation of these two liquids as well as any clays, straws, sawdust, etc. with which these fluids are associated. Thus, large volumes of oil-contaminated water must be physically handled and chemically treated, in closed vessels, in order to successfully capture those relatively small volumes of oil associated with the oil-contaminated water. The expense of handling and treating such large volumes of water is enormous. Worse yet, the time needed to take up and treat such large volumes of water and its associated oil is painfully long when viewed from the standpoint that the spilled oil is relentlessly damaging the environment while simultaneously becoming more and more difficult to recover as it becomes more and more dispersed with the passage of time.
Some representative methods for using clays to convert oil films and/or oil/water emulsions into larger oil droplets and patches in order to facilitate subsequent oil/water separation operations are taught in the following patent references which are each incorporated by reference into this patent disclosure.
U.S. Pat. No. 3,634,227 generally teaches use of various clays such as attapulgite, bentonite, and kaolin to agglomerate spilled oil in order to facilitate its collection from the surface of the water.
U.S. Pat No. 2,531,427 teaches that clays of the same type employed by applicants can be substituted with amine groups to produce "organoclays" which are generally capable of forming stable gels and colloidal dispersions in various industrial processes. In general, the amine-treated clays taught by this reference constitute the same kinds of "organoclays" employed by applicants in their processes.
U.S. Pat. No. 4,778,627 teaches a process for disposing of radioactive liquid hydrocarbons by adding an organic ammonium montmorillonite clay to such liquids in quantities sufficient to produce a solid waste product.
U.S. Pat. No. 3,948,770 teaches that mixtures of finely dispersed oil droplets and sea water, and especially those present in oil tanker compartments, can be separated through the use of a flocculating agent comprised of a dry powered mixture of an anionic polyelectrolyte, such as an anionic copolymer of acrylamide, and a montmorillonite clay. This reference also notes that when small quantities of oil are finely dispersed within a relatively large body of water--a situation typically found in the slop tanks of large oil tankers--separation of those fine droplets of oil is normally extremely slow and that a much more rapid agglomeration into a distinct oil phase may be obtained by use of the therein disclosed anionic polyelectrolyte/clay mixture.
U.S. Pat. No. 4,473,477 ("the 477 patent") teaches that certain organoclays of the same type employed in applicants' patent disclosure can be used to solidify fluid waste materials in retention ponds or lagoons designed to hold such fluid waste materials. Typically the fluid wastes are contained by an impermeable liner which forms the bottom and sides of the waste pond. This reference also teaches that an adjunct bed of such organoclays can be employed in order to capture certain organic contaminants before they enter local ground waters. Thus, a contaminated fluid flowing through these beds will have its associated organic materials removed by the bed so that the resulting leachate (e.g., water) can be safely released into the environment.
In another embodiment of the invention described in the 477 patent (which embodiment is discussed from column 7, line 56 to column 8, line 3 of this reference), an organoclay is sprayed on an artificial lagoon containing an oil-contaminated fluid such as water. In this particular embodiment, the organoclays are added in quantities such that the organoclay sorbs the oil and forms agglomerate clumps which sink to the bottom and/or sides of the lagoon in order to produce an impermeable layer or liner "plug" which serves to stop the flow of oil-contaminated water into local ground waters.